The Similarities and Differences Between SEM and TEM

While each microscope utilizes electrons rather than light to gather a higher image resolution, the methods differ in detail.

What are the Similarities?

Both TEM and SEM share several key components:

  • Multiple electrostatic and electromagnetic lenses are involved in managing the trajectory and shape of the electron beam.
  • An electron source.
  • The sample chamber is placed under high-vacuum.
  • Electron apertures.

What are the Differences?

  • TEM enables data to be captured regarding the sample’s inner structure, where SEM provides data about the surface of the analyzed object.
  • TEM offers a greater resolution compared to SEM.
  • In comparison to SEM, TEM has more stringent requirements concerning the preparation of samples and the conditions of analysis.

Electron microscopy images of silicon. a) SEM image with SED offers information on the morphology of the surface, while b) TEM image reveals structural information about the inner sample.

Electron microscopy images of silicon. a) SEM image with SED offers information on the morphology of the surface, while b) TEM image reveals structural information about the inner sample. Image Credit: Thermo Fisher Scientific Phenom-World BV

Overview: Scanning Electron Microscopy (SEM)

Since electron microscopes were first introduced in the 1930s, SEM has evolved into a highly powerful mechanism within many varied research fields, from forensics to materials science, and from life sciences to industrial manufacturing.

The key reason for this popularity growth can be linked to the constant shrinking of the dimension of materials utilized in a range of applications.

How exactly does an SEM function, and what needs to be known about this technology? This article aims to answer the most frequently asked questions regarding SEM.

What is SEM?

An SEM is a kind of electron microscope that employs an electron beam for scanning the sample. The electrons that are backscattered, along with the ones that are knocked off the object’s near-surface area, are identified and utilized to produce high-resolution images.

How Does it Work?

Also known as an electron gun, an electron source generates electrons that are accelerated by an applied voltage. Magnetic lenses converge the electron stream into a focused beam, which then reaches the surface of the sample in a small, accurate location.

The surface of the specimen is scanned by the electron beam in a rectangular raster. The user can enhance the magnification by decreasing the size of the scanned region on the specimen.

Detectors acquire the backscattered and secondary electrons (SE). The related signals are analyzed and the values are traced as changes in brightness on the image display.

The secondary electrons are more commonly utilized as a read-out signal. They visualize the topography of the surface of the sample: the bright areas signify edges whereas dark areas signify recesses.

For What Purposes and Specimen Can SEM be Applied?

SEM becomes an essential tool when microscopic data about the surface or near-surface area of a particular specimen is necessary. For this reason, the technique finds applications in almost all fields within technology, industry, and science.

The only apparent limitation is that the observed object must be able to cope with the vacuum inside of the chamber and the bombardment of electrons.

This information has been sourced, reviewed and adapted from materials provided by Thermo Fisher Scientific Phenom-World BV.

For more information on this source, please visit Thermo Fisher Scientific Phenom-World BV.

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